Lab 5

Georgia Institute of Technology School of Civil and Environmental Engineering Compaction Limits Laboratory MEMORANDUM To: Emre Duman Date: March 8, 2023 From: Sachinshripadh Dasu, A3-1 Lab Partners: Stephen Grafius, Marty Robert James Jr., Ashley Eun Joo Jhun Subject: CEE 3400 Sample(s) Description: Name: Piedmont Red Clay Source: In-Situ Condition: Dry Visual Classification and Unified Symbol: SM Remarks: Piedmont Red Clay was used as a soil sample for this laboratory experiment. Test Procedure: Test Procedures: ASTM D698: Standard Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort (12,400ft-lbf/ft3 (600 kn-m/m^3) ASTMS D1557: Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft^3 (2700 kn-m/m^3) The Compaction laboratory is based on ASTM D698 and ASTM D1557. There were two experiments performed in this laboratory: The standard test and the modified test. The procedures in this laboratory were followed as detailed in the laboratory handout and there were no deviations. First, roughly 4.3kg of air -dried soil is obtained and sieved through a U.S. No. 4 sieve. Then, water is added and mixed in with the soil to bring the moisture content up to about 6% below the estimated optimum moisture content. The mass of the Proctor mold and base plate are also recorded. The wet soil is then added to the mold. For the standard test method, the soil is filled to slightly over halfway of the mold, and for the modified test method, the soil is filled to about 1/3 of the height of the mold. After the soil has been added, the hammer is gently placed into the mold and is hammered down into the soil 25 times. After compaction, the excess soil on the mold is trimmed and the mass of the mold, base plate, and compacted soil is recorded. Then, the compacted soil cylinder is removed from the mold and more water is added to raise the moisture content by about 3%. These steps are repeated until at least two successful down readings are obtained. Then, all of the containers with soil are placed in the oven to dry to a constant weight. After 24 hours, the mass of the container and dry soil samples are also recorded.

Test Results: 1. The figure below, Figure 1, plots the dry unit weight vs. the water content curves for both the standard and modified test methods with all of the class data on the same graph. The maximum dry unit weight and the optimum water content for both the standard and modified tests are also shown below in Table 3. Sample calculations for the water content and dry unit weight are also shown below. 8 10 12 14 16 18 20 22 24 26 28 0 2 4 6 8 10 12 14 16 18 20 standard modified Water Content (%) Dry Unit Weight (kN/m3) Figure 1. Dry Unit Weight (kN/m3) vs. Water Content (%) Curves. Standard Modified Maximum Dry Unit Weight 16.6 18.4 Optimum Water Content 18.9 13 Table 1. Maximum Dry Unit Weight and Optimum Water Content for Standard and Modified Tests. Sample Calculations: Dry Unit Weight = ( Mass of Compacted Soil Volume of Mold ) ∗ g ∗ ( 1 1 + water content ) = ( 1678 943.7 ) ∗ 9.81 ∗ ( 1 1 + .111 ) = 15.71 kN / m 3 Water Content = Mass of Water Mass of Dry Soil ∗ 100 = 2.1 19.4 = 11.1% 2. The figure below, Figure 2, plots the zero-air void (ZAV) line for 100% saturation on the same graph as the compaction curves for both tests. Sample calculations for calculating the zero-air void line are also shown below.

samples to compact irregularly and there could have been a few instances where the hammer did not completely drop on the soil samples. The human error when removing the extension collar from the mold could have ben an issue as some of the compacted soil inside the mold could have been broken off. Additionally, the human error when mixing water into the soil sample could have caused errors as the soil sample could have been over or undersaturated. This would have caused issues when compacting the soil sample in the mold. There are several engineering applications that rely on this test. This is very important to civil and geotechnical engineers as it is crucial to determine the optimal moisture content and maximum dry unit weight of a soil sample. These values can be crucial to construction as well as it is important to understand the soil that anything is being built on top of. The Proctor test can also be used in road construction to determine the compaction of the roads. It is also important for many earth works projects such as dams. The use of a heavier hammer and more layers affects the measured maximum dry unit weight and the optimum water content as a heavier hammer would cause an increase on compaction. This would yield in a lower optimum moisture content and a higher maximum dry unit weight for the soil. If these test results were part of a real geotechnical report for a project, the values of the dry unit weight and the water content would typically be 16-18 kn/m3 and 10-25%, respectively. The range of values would vary based on the specific project requirements. For example, if a project required a soil sample with higher compaction, the modified test standard would be more appropriate than the standard test. Concluding Remarks : The purpose of Compaction laboratory is to determine the dry unit weight and water content of a compacted soil sample, as well as to determine the zero-air void curve for 100% saturation of the soil sample. It is often necessary to compact soil to improve its strength. The degree of compaction of a soil is measured by its dry unit weight 𝛾𝑑 . When water is added to the soil during compaction, it acts as a softening agent on the soil particles. The particles slip on each other and move into a densely packed position. For similar compacting efforts, the dry unit weight of compaction increases as the moisture content increases. However, beyond a certain moisture content 𝑤 = 𝑤𝑜 pt, any increase in moisture content tends to reduce the dry unit weight. This is because the water takes up the spaces that would have been occupied by the solid particles. The moisture content at which the maximum dry unit weight ( 𝑚 ax) is attained is generally referred to as the optimum moisture content (i.e., 𝑤𝑜 pt). Proctor (1933) developed a laboratory compaction test procedure to determine the maximum dry unit weight of compaction of soils that can be used for the specification of field compaction. This test is referred to as the standard Proctor compaction test and is based on the compaction of the soil fraction passing a U.S. No.4 sieve. ASTM Standard D-1557 provides a modified method to conduct the Proctor compaction test. The test is conducted with a 10 lb (44.5 N) hammer. A comparison of compacted density versus water content curves obtained from standard and modified Proctor compaction tests show that the maximum dry unit weight of compaction increases with the increase in the compacting energy, and the optimum moisture content decreases with the increase in the energy of compaction. The tests were able to relatively achieve the desired results, as shown in the Test Results section of this laboratory report. The only limitation of the work is that the Proctor test is not as versatile in the field as it is in the laboratory, and the test requires specialized resources and can be time consuming. There are several engineering applications that rely on this test. This is very important to civil and geotechnical engineers as it is crucial to determine the optimal moisture content and maximum dry unit weight of a soil sample.

These values can be crucial to construction as well as it is important to understand the soil that anything is being built on top of. The Proctor test can also be used in road construction to determine the compaction of the roads. It is also important for many earth works projects such as dams. References: Dai, S. (2024, February 29). Lab 5 – Compaction.pdf. Hirebelaguly Shivaprakash, S., & Sridharan, A. (2021). Correlation of compaction characteristics of standard and reduced Proctor tests. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering , 174 (2), 170–180. https://doi.org/10.1680/jgeen.20.00060 Reznik, Y. M. (1995). Comparison of results of oedometer and plate load tests performed on collapsible soils. Genesis and Properties of Collapsible Soils , 383–408. https://doi.org/10.1007/978-94-011-0097-7_21